Vortex Electromagnetic Wave Research Articles

Mode Measurement of Vortex Electromagnetic Wave With Random Receiving Array Element Defects via Low Rank Matrix Completion

Mode Measurement of Vortex Electromagnetic Wave With Random Receiving Array Element Defects via Low Rank Matrix Completion

A position-based method for detecting orbital angular momentum modes

Abstract Due to the inherent limitations of current Orbital Angular Momentum (OAM) mode detection methods and constraints posed by the physical size of receiving antennas, accurately identifying higher-order OAM modes represents a significant challenge. Therefore, there is a pressing necessity to overcome these hurdles. This paper introduces a new approach to OAM mode detection that exploits positional information. Our methodology ascertains the OAM mode by examining the phase and position data of the electric field at any two randomly chosen points within the energy's spatial distribution radiated by vortex electromagnetic waves. This innovation promises not only to precisely detect higher-order OAM modes but also grants greater versatility in the placement of receiving antennas. Moreover, the study delves into the correlation between the electric field phase of vortex electromagnetic waves, the azimuth angle, and the receiving distance. The validity of our approach is confirmed through both simulation outcomes and experimental data derived from physical tests.

Three-Dimensional Interferometric Imaging With Vortex Electromagnetic Wave Radar Based on Uniform Circular Array

Three-Dimensional Interferometric Imaging With Vortex Electromagnetic Wave Radar Based on Uniform Circular Array

Gravitational orbital Hall effect of vortex light in Lense–Thirring metric

Vortex light, characterized by an intrinsic orbital angular momentum aligned with its propagation direction, is described through vortex electromagnetic waves. Similar to the gravitational spin Hall effect (SHE), vortex light is expected to exhibit intrinsic orbital angular momentum dependent trajectories and deviations from the null geodesic plane when propagating through a gravitational field, a phenomenon termed the gravitational orbital Hall effect (OHE). In this work, we model the vortex light as vortex Laguerre–Gaussian electromagnetic wave packets and analyze its motion by solving covariant Maxwell equations within the Lense–Thirring metric. Our findings reveal that the trajectory of vortex light with an intrinsic orbital angular momentum deviates from the null geodesic in two ways. It deviates both perpendicular to, and within, the null geodesic plane. This behavior contrasts with the gravitational SHE, where spin-polarized light primarily deviates perpendicular to the null geodesic plane. Moreover, the relationship between the deviation and intrinsic orbital angular momentum differs significantly from that between the deviation and spin. These results suggest a unique interaction between intrinsic orbital angular momentum and gravity, distinct from the spin-gravity coupling, indicating that the gravitational OHE of light might not be precisely predicted by merely substituting spin with intrinsic orbital angular momentum in the gravitational SHE of light.

Multipath Characteristics of Orbital Angular Momentum Vortex Electromagnetic Radio Waves Over an Infinite Ground Plane

In this paper, the effect of an infinitely sized ground plane on the orbital angular momentum (OAM) vortex electromagnetic (EM) radio waves is investigated. Although the effect of an infinite ground on OAM wave propagation and communication has already been numerically examined in the literature using the method of moments (MoM), this situation needs to be examined analytically and theoretically derived final form expressions need to be obtained. The multipath characteristics of OAM waves in a superconducting ground plane are theoretically presented considering both horizontal and vertical polarization conditions. In addition to direct radiation to an observation point in the far-field from the array antenna, many reflected radiations from the ground plane are also transmitted. The most fundamental reflected radiation is analyzed over a uniform circular array (UCA), adopting electromagnetic image theory. Furthermore, the transmitted field expressions obtained by considering both the circular array parallel to the ground plane and the circular array upright to the ground plane are formulated in a general analytical form for an OAM wave on a superconducting ground plane. In addition, numerical simulations are applied to exemplify the properties of OAM waves in the superconducting ground plane, unlike the isolated medium.

Micro‐motion parameters extraction of rotating target based on analytical solution in vortex electromagnetic wave radar

AbstractThe linear Doppler effect and angular Doppler effect in vortex electromagnetic wave radar echoes can be used to extract comprehensive micro‐motion parameters. However, the analytical solution of micro‐motion parameters for rotating targets in vortex EM wave radar has not been obtained. To solve the above problems, the analytical solution of micro‐motion parameters is derived, and a micro‐motion parameter extraction method is proposed. Firstly, the shape and properties of the angular Doppler curve in various cases are discussed. Subsequently, the properties of three points on the angular Doppler curve are derived. The micro‐motion parameters are obtained based on the three points. The simulations demonstrate that the proposed method can greatly reduce the computational complexity and improve the accuracy of micro‐motion parameter extraction.

A Vortex Electromagnetic Wave Beam Control Method based on Amplitude-Modulated Concentric Circular Array

Abstract In order to enhance the design efficiency of vortex electromagnetic (EM) wave radar detection systems, a method for generating and controlling vortex EM waves based on amplitude-modulated concentric circular array (CCA) is proposed. This method allows for precise control of the vortex EM waves, ensuring accurate main lobe direction while effectively reducing sidelobes. Based on approximate orthogonal transformation, formulas for calculating the excitation amplitudes of each sub-circular array are derived and the time complexity of this method is negligible compared to search-based algorithms. Extensive simulation experiments are conducted and compared with the results obtained from the genetic algorithm (GA) approach, providing robust evidence of the effectiveness of this method(SLL < -30dB).

Suppression of vortex electromagnetic wave divergence by modulating the wave front dislocation line

Abstract When the beam is transmitted in the atmosphere, under the influence of atmospheric turbulence, the beam will occur energy attenuation, wavefront distortion and other phenomena, which will seriously affect the transmission and reception of information. Based on the PB phase principle enhances the focusing capability of the auto-focusing Airy Gaussian vortex beam by regulating the wavefront error curvature of the vortex beam, and then enhances the resistance of the beam against atmospheric turbulence. The results reveal the curvature of the wavefront error curve and the peak intensity of the light field of the beam can be changed by changing the beam polarization state parameters n and m in the focal plane. The auto-focusing Airy Gaussian vortex beam with the polarization state parameters m=1, n=4 increases the peak magnitude of the light field intensity in the focal plane of the auto-focusing Airy Gaussian vortex beam with the polarization state parameters m=0, n=0 to 1.99 times. Demonstrate that geometric phase tuning the auto-focusing Airy Gaussian vortex beams can enhance resistance to atmospheric turbulence. Furthermore, this paper extends this method to the field of millimeter wave. Under the transmission distance of 1km, the peak intensity of the initial vortex electromagnetic wave after the geometric phase adjustment is increased to 3.33 times, and the receiving radius of the target surface is reduced to 0.24 of the initial vortex electromagnetic wave. It shows that geometric phase-regulated vortex electromagnetic wave can suppress vortex electromagnetic wave divergence and have potential applications in wireless communication.

Terahertz vortex beam generation based on reflective and transmissive graphene metasurfaces

Graphene metasurfaces have substantial potential for generating vortex electromagnetic waves carrying orbital angular momentum (OAM) at terahertz frequencies. In this paper, a deformed H-shaped graphene unit cell is utilized to design a half-space reflective metasurface (with a metal backplane, operating in the reflection mode) and a full-space metasurface (operating in both the reflection and transmission modes) to generate OAM beams. The two structures are intertransformable at the level of physical composition, where one configuration enables efficient anomalous reflection of electromagnetic waves within the 4.6–8.9 THz band, while the other enables uniform modulation efficiency of reflective and transmissive waves within the 5.5–7.0 THz band. Equivalent circuit models have been provided to establish a convenient closed-form mathematical description of the metasurface’s electromagnetic behavior. By performing the near- and far-field simulations, a series of THz vortex generators based on the proposed graphene metasurface are demonstrated. In particular, high-purity reflective and transmissive OAM waves with distinct topological charges are observed. Our study provides a path towards the practical realization of active THz OAM metadevices.

Parameter Extraction of Accelerated Moving Targets under Non-Quasi-Axial Incidence Conditions Based on Vortex Electromagnetic Wave Radar

Vortex electromagnetic wave radar carrying orbital angular momentum can compensate for the deficiency of planar electromagnetic wave radar in detecting motion parameters perpendicular to the direction of electromagnetic wave propagation, thus providing more information for target recognition, which has become a hot research field in recent years. However, existing research makes it difficult to obtain the acceleration and rotation centers of targets under non-quasi-axial incidence conditions of vortex electromagnetic waves. Based on this, this article proposes a variable speed motion target parameter extraction method that combines single element and total element echoes. This method can achieve three-dimensional information extraction of radar targets based on a uniform circular array (UCA). Firstly, we establish a non-quasi-axis detection echo model for variable-speed moving targets and extract echoes from different array elements. Then, a single element echo is used to extract the target’s range slow time profile and obtain the target’s rotation center z coordinate. We further utilize the target linear, angular Doppler frequency shift extremum, and median information to extract parameters such as target acceleration, tilt angle, rotation radius, and rotation center x and y coordinates. We analyzed the impact of different signal-to-noise ratios and motion states on parameter extraction. The simulation results have verified the effectiveness of the proposed algorithm.

2-битные метаповерхности Патчаратнама-Берри с генерацией, интерференцией и гашением орбитального углового момента для широкополосного снижения ЭПР

The radar cross-section (RCS) reduction using non-absorbing digital Patcharatnam-Berry (PB) metasurfaces (MSs), consisting of 2-bit modules with generation, interference and cancellation of vortex electromagnetic waves with orbital angular momentum (OAM) is studied. Each module has a helical PB-phase profile and possesses vortex scattering. Module unit cells contain a shielded dielectric substrate and meta-particles in the form of triple-coupled split-ring resonators. The modules are distinguished by 2-bit coding of the initial tilt angle of the meta-particles 0º, 45º, 90º and 135º. The purpose of the work is to numerically analyze the generation of antiphase vortex beams (VBs) by OAM-modules and to assess the influence of interference and cancellation of antiphase vortices on the structure and order of OAM in the resulting field and the RCS reduction of three digital MSs in the form of 2´2 lattice of 2-bit OAM-modules of different sizes with different topological charges. The scattering characteristics are studied using HFSS for normally incident circularly polarized waves using of the finite element method. The simulation showed that the interference of phase vortices of four OAM-modules forms the main axial vortex and N additional interference side near and far vortices (N depends on the size of the MS). Interference vortex beams create phase singularities and zero the resulting far field in N side directions over the entire forward hemisphere. The intense OAM modes of the main vortex beams are of the fourth or eighth order. The OAM modes of adjacent interference VBs, as a rule, differ in sign. The proposed 2-bit MSs provide wider-angle phase cancellation of vortex fields (compared to 1-bit MSs) and, as a consequence, wider-angle diffuse scattering of the resulting field of the MS, which is important for RCS reduction.

Vortex electromagnetic wave imaging with orbital angular momentum and waveform degrees of freedom

The vortex electromagnetic wave has shown great prospects of radar applications, due to the orbital angular momentum (OAM) degree of freedom. However, the radiation energy convergence of the OAM beam remains a hard problem to be solved for radar target imaging in realistic scenario. In this paper, an OAM beam generation method is developed exploiting the OAM and waveform degrees of freedom simultaneously, which can collimate the beams with different OAM modes. Furthermore, the echo demodulation and the imaging methods are proposed to reconstruct the target profiles in the range and azimuth domain. Simulation and experimental results both validate that the OAM-based radar imaging can achieve azimuthal super-resolution beyond the diffraction limit of the array aperture. This work can advance the system design of vortex electromagnetic wave radar and its real-world applications.

Photonics-Based Broadband Vortex Electromagnetic Wave Generation for High-Resolution Imaging

Photonics-Based Broadband Vortex Electromagnetic Wave Generation for High-Resolution Imaging

3-D ISAR Imaging via Migration Through Azimuthal Angle Cell Compensation With Vortex Electromagnetic Wave Radar

3-D ISAR Imaging via Migration Through Azimuthal Angle Cell Compensation With Vortex Electromagnetic Wave Radar

Analysis and Design of Broadband OAM Array Antenna

This paper presents a Uniform Circular Array (UCA) antenna of crossed-dipole that can excite vortex waves in a wide frequency range from 3.5 GHz to 8.4 GHz. In the design process, the theoretical derivation of the influence on the Orbital Angular Momentum (OAM) when the antenna elements are arrayed in Co-directional Antenna Array (CAA) and Rotational Antenna Array (RAA) is given respectively. The fixed mode of the dipoles CAA is achieved by feeding each element with equal amplitude and 90∘ phase difference produced by the broadband feeding network. Furthermore, the proposed broadband OAM array antenna has been fabricated and measured to verify the predicted properties. The vortex electromagnetic wave with +1 mode could be excited in the bandwidth of 82.35%. Simulated and measured results are in good agreement. The proposed OAM array antenna is simple in design principle, compact in structure and low in profile, making this array antenna an excellent candidate for broadband OAM communication systems.

Correction: Extinction efficiency and scattering asymmetry of a PEMC sphere illuminated by vortex electromagnetic waves

Correction: Extinction efficiency and scattering asymmetry of a PEMC sphere illuminated by vortex electromagnetic waves

A Novel Forward-Looking Target Reconstruction Method With Electromagnetic Vortex Interferometry

For the target in the radar forward-looking sight, only the range-history phase information can be exhibited when the plane electromagnetic (EM) wave illuminating. For traditional approaches, the reconstruction of target azimuthal information requires antennas configured at both ends of the long baseline to implement multi-angle observation, usually leading to a baseline length burden. In contrast, the target’s azimuth information, related to the orbital angular momentum (OAM), is directly modulated in the new-dimensional echo phase by the antenna radiating the vortex EM wave, which provides a new foundation for target azimuth reconstruction. In this article, a novel forward-looking target reconstruction methodology with EM vortex interferometry is proposed, and the target 3-D imaging with different OAM modes interferometry strategies is achieved as well. The developed approach can improve the target azimuthal reconstruction error performance without increasing the length of short baseline and image registration. Comprehensive results of simulated data and real-world measured data are performed to validate the effectiveness and anti-noise robustness of the proposals.

Detection accuracy of target accelerations based on vortex electromagnetic wave in keyhole space

The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed. The spectrum spreads of different orbital angular momentum (OAM) modes in different non-line-of-sight situations are simulated. The errors of target accelerations in detection are calculated and compared based on the OAM spectra spreading by using two combinations of composite OAM modes in the keyhole space. According to the research, the effects about spectrum spreads of higher OAM modes are more obvious. The error in detection is mainly affected by OAM spectrum spreading, which can be reduced by reasonably using different combinations of OAM modes in different practical situations. The above results provide a reference idea for investigating keyhole effect when vortex electromagnetic wave is used to detect accelerations.

Extinction efficiency and scattering asymmetry of a PEMC sphere illuminated by vortex electromagnetic waves

Extinction efficiency and scattering asymmetry of a PEMC sphere illuminated by vortex electromagnetic waves

SAR Imaging Based on OAM‐ωK Algorithm

AbstractTraditional radar imaging was restricted by the antenna aperture and imaging scene. It was difficult to improve azimuth resolution greatly. The vortex electromagnetic (EM) waves carrying orbital angular momentum have a special helical phase wavefront structure. The vortex EM waves could bring more degrees of freedom when applied to synthetic aperture radar imaging, make it possible for ultra‐high resolution imaging, provide a new possibility for the bottleneck problem of azimuth resolution in traditional radar imaging. In this paper, an OAM‐ωK algorithm was used to compensate the Bessel term and residual azimuth angle term which in the echo signal. Because the azimuth term and azimuth angle term were fused into a new azimuth term, the Doppler bandwidth was broadened and high resolution imaging was achieved. The theory verified the advantages of the algorithm in azimuth resolution. By comparing simulation experiments of single target point and multi‐target points with the traditional ωK algorithm, the proposed OAM‐ωK algorithm had higher azimuth resolution, proving the algorithm’s effectiveness.